Bodhi Day is a Buddhist holiday that commemorates the day that Siddhartha Gautama experienced bodhi (enlightenment). Its date varies from country to country. In Japan, Bodhi Day has been celebrated on December 8 since the introduction of the Gregorian calendar.

According to Buddhist tradition, Siddhartha Gautama (the historical Buddha) attained enlightenment at the age of 35 after 49 days of meditation under a sacred fig tree, now known as the Bodhi tree. Gautama found the cause of suffering and realized the steps necessary to liberate oneself from it. Buddha's enlightenment is believed to have occurred in the 5th or 12th lunar month.

In Japan, Bodhi Day is also known as Rōhatsu. It was originally celebrated on the 8th day of the 12th month of the lunisolar calendar. When Emperor Meiji began the westernization of Japan and introduced the Gregorian calendar, the celebration was moved to December 8.

Bodhi Day is not an official holiday in Japan. It is celebrated only by Buddhists, who comprise about 34% of the country's population. Zen monks usually stay up the entire night before the festival meditating. The traditions of commemoration may vary, but the most common ones include meditation, chanting of sutras, performing acts of kindness, etc.